Asked about United's success in Europe despite their domestic woes, Muelensteen told Tipman Tips: "There are two scenarios. If they win [the Europa League] then there’s more money, Champions League football, and a positive feeling that they can do something next season. If they don't win, they have no European football and no extra money coming in. It would mean that they’ll be sitting with the same squad and the same manager, going into next year.
"Take Bruno Fernandes out of that team then you are looking at a really bleak scenario there.
"Amorim should have done better because he's had plenty of time now working with the players, and you question the disconnect when you constantly see these poor performances. Do they lack quality? Are the messages not getting across to the players? Or is it the rigid system?
"At the end of the day, why have Man United been able to turn up many times in the Europa League but not once in the Premier League for the last few months? It’s because the coach lacks experience, you know, in terms of managing a club the size of Manchester United.
"When you predominantly have the same team, manager, and don’t change the system, why would it be any different next season? They’re in major trouble if they lose."